NEW YORK (Reuters Health) - Overweight moms who lose weight after their first baby are less likely to develop diabetes during their second pregnancy, a new study shows.

The researchers found the reverse was also true: all women - overweight or not -- who gained weight between pregnancies had a better chance of developing diabetes during their second pregnancy than women whose weight remained stable.

Samantha Ehrlich, the research project manager at the Division of Research at Kaiser Permanente and the lead author on the study, said she was not surprised by the results.

"A lot of people have shown that lifestyle intervention to help people lose weight can delay the onset of type 2 diabetes" in adults who are not pregnant, Ehrlich told Reuters Health.

Being overweight is a risk factor for developing pregnancy-related diabetes, called gestational diabetes, which affects four percent of pregnant women.

Babies whose mothers have gestational diabetes tend to be larger, and mothers are at greater risk for high blood pressure.

Ehrlich and her colleagues examined medical records covering a 10-year period for more than 22,000 women who had their first and second babies using Kaiser Permanente Northern California facilities.

Forty-six out of every 1,000 women had gestational diabetes during their first pregnancies, 52 out of every 1,000 had it during their second pregnancies, and 18 out of every 1,000 mothers developed diabetes during both pregnancies.

The risk of developing diabetes during the second pregnancy among all the women increased with the amount of weight gained after the first baby.

For example, a 5'4'' woman who starts out at a normal weight (up to 145 pounds) and gains six to 12 pounds between pregnancies is almost twice as likely to develop gestational diabetes during her second pregnancy than a similar woman who has not gained weight.

If that same mom gains more than 18 pounds between pregnancies, her risk of gestational diabetes quadruples for her second pregnancy.

The increased risk associated with weight gain between pregnancies was also evident for women who were overweight or obese during their first pregnancy, but the rise was not as steep as for women who were of normal weight.

Dr. Eduardo Villamor at the University of Michigan, who was not involved in the study, has found previously that the risk of gestational diabetes during a second pregnancy increased with the amount of weight women gained after the first one.

"The message is that women should maintain a healthy weight before and after pregnancy," Villamor told Reuters Health in an email.

The current study, which is published in the journal Obstetrics and Gynecology, adds new information about the effect of weight loss on the risk of gestational diabetes.

Losing weight between pregnancies was tied to a reduced risk of diabetes for the second pregnancy, but only among overweight women.

A 5'4'' tall woman who is, for instance, 160 pounds during her first pregnancy, then loses six pounds, cuts her diabetes risk by 38 percent for her second pregnancy.

Is she loses more than 12 pounds, her gestational diabetes risk during the second pregnancy is 75 percent smaller than if her weight had remained the same.

"We thought that these findings indicated for all women that they should get back to their pre-pregnancy weight or lose weight if they were overweight or obese pre-pregnancy," Ehrlich said.

Ehrlich and her colleagues have reported success with a pilot program to help women lose weight after having a baby, but she says she understands the challenge some moms face in getting back the pre-baby body.